Intestine Specific Homeobox Protein (ISX)

Using expression profiling to identify transcription factors involved in development of the mouse digestive tract, Choi et al. (2006) identified a novel gene, which they they named Isx because of its highly restricted expression pattern in the intestine.This construct showed that Isx is abundantly expressed in intestinal epithelial cells from the duodenum to the proximal colon. Expression profiling showed further that beta-carotene 15,15-prime-monooxygenase (BCMO1) and Scarb1 were highly upregulated in homozygous knockout animals. BCMO1 is involved in vitamin A synthesis and SCARB1 in carotenoid and cholesterol uptake. Vitamin A deprivation of wildtype mice resulted in decreased Isx and increased Bcmo1 expression. Isx participates in vitamin A metabolism most likely by regulating Bcmo1 expression in the intestine.